Method sendfile

3rdparty/libprocess/src/posix/poll_socket.cpp:242–287

Future<size_t> PollSocketImpl::sendfile(int_fd fd, off_t offset, size_t size)
{
  CHECK(size > 0); // TODO(benh): Just return 0 if `size` is 0?

  // Need to hold a copy of `this` so that the underlying socket
  // doesn't end up getting reused before we return.
  auto self = shared(this);

  return loop(
      None(),
      [self, fd, offset, size]() -> Future<Option<size_t>> {
        while (true) {
          Try<ssize_t, SocketError> length = os::sendfile(
              self->get(),
              fd,
              offset,
              size);

          if (length.isSome()) {
            CHECK(length.get() >= 0);
            return length.get();
          }

          if (net::is_restartable_error(length.error().code)) {
            // Interrupted, try again now.
            continue;
          } else if (!net::is_retryable_error(length.error().code)) {
            VLOG(1) << length.error().message;
            return Failure(length.error());
          }

          return None();
        }
      },
      [self](const Option<size_t>& length) -> Future<ControlFlow<size_t>> {
        // Retry after we've polled if we don't yet have a result.
        if (length.isNone()) {
          return io::poll(self->get(), io::WRITE)
            .then([](short event) -> ControlFlow<size_t> {
              CHECK_EQ(io::WRITE, event);
              return Continue();
            });
        }
        return Break(length.get());
      });
}

} // namespace internal {
} // namespace network {